Computing moves on and it becomes harder and harder to bolt improvements on to a clunky old chassis without cutting and welding. Why would any company do that if you aren't paying for it?
MG32, seriously, why would MS care? Those companies are probably too wedded to other MS products to change to anything different. If they really want to keep using XP they can start writing large cheques for the privilege of continued support or take their chances......
It's not like they haven't had however many years warning to plan a transition.